Silver is contained in a fluid waste product generated during traditional photographic film development processes. Such processes are currently used in a variety of industries, including but not limited to the health care industry, as in the development of radiological film, the print media industry, as in the development of photographs on film to be printed in publications such as newspapers, and in the commercial development of photographs taken on film by the general public. Regulations promulgated and enforced by the U.S. Environmental Protection Agency require that the concentration of silver in fluids drained into the environment as waste be limited to 5 parts per million. However, industry routinely fails to comply with this regulation, frequently draining fluids into the environment that contain hundreds and even thousands of parts per million of silver.
This compliance failure is typically caused by use of primitive silver recovery and monitoring systems. One such primitive system is a bucket of steel wool in which raw photographic fixer fluid containing silver is collected and filtered before being drained into the environment. In the ideal case, in such systems the iron atoms in the steel wool react with the silver ions in the fixer fluid to replace the steel wool with solids of silver and silver compounds, causing the resulting iron ions to flow out of the system into the environment with fluid containing no more than 5 parts per million of silver. However, in practice, such systems rarely if ever result in compliant drain fluid because the actual silver concentration in the fluid drained into the environment is never monitored, and the steel wool is spent very quickly, thereby causing unfiltered, high-silver-concentration, noncompliant fixer fluid to be drained into the environment.
A system and method for silver recovery and monitoring is disclosed below.